This happened to staff at O2 and EADS in the past, although their bans may have since been lifted.
If you find yourself banned, and desperately need your access to TT, try installing the ErrorZilla Plus add-on. Note, this only works for the Firefox browser.
ErrorZilla Plus 0.3.1
QUOTE
This extension is a mod of the ErrorZilla Mod extension. I added a "Proxify" function into it. When error page shows, you can choose a web proxy from a list and browse the unreachable network address via it.
Take care when sending PMs via the proxy, however. You might run into trouble with hundreds of copies of the same PM being sent.